1. Field of the Invention
The present invention relates to a wide-angle lens system having a long back focal distance suitable for an electronic still camera.
2. Description of the Prior Art
In an electronic still camera which utilizes a solid-state image sensor such as a CCD, miniaturization and higher definition of imaging devices have progressed, and accordingly, a wide-angle lens system having a short focal length has become increasingly in demand. In addition, in such an electronic still camera, in order to provide optical elements, such as a low-pass filter, an infra-red filter, and a beam splitter, etc., between the photographing lens system and the imaging device, a long back focal distance is required. However, in a wide-angle lens system, it is difficult to obtain both a long back focal distance and a desirable optical performance.